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Agricultural  Experiment  Station 


BULLETIN  No.  181 


BY  J.  G.  MOSIEE  AND  A.  F.  GUSTAFSON 


URBANA,  ILLINOIS,  APRIL,  1915 


SUMMARY  OF  BULLETIN  No.  181 

I.  A  deep,  well-prepared  seed  bed  is  essential  for  aeration,  proper  root  devel- 
opment, and  conservation  of  moisture.    It  gave  a  gain  of  14.5  bushels  ($7.25  at 
50  cents)  per  acre  over  no  seed  bed.     (Table  6.) 

1  2.  Killing  weeds  is  the  most  important  factor  in  cultivating  corn  on  brown 
silt  loam.  No  weeds  gave  an  increase  over  weeds  of  38.6  bushels  of  corn,  a  gain 
of  $19.30  per  acre.  (Table  6.) 

^  3.  Weeds  reduce  the  yield  of  corn  more  by  robbing  it  of  plant  food  and  light 
than  by  depriving  it  of  moisture.  Irrigation  on  a  weed  plot  gave  an  increase  of 
only  3.8  bushels.  (Table  6.) 

'  4.  As  an  average  of  sixteen  tests  in  eight  years,  killing  weeds  without  cul- 
tivation produced  a  gain  of  17.1  percent,  or  6.7  bushels  per  acre,  over  ordinary  cul- 
tivation. (Table  6.) 

5.  Three-fourths  of  the  corn  roots  are  in  the  plowed  soil,  and  as  plants  de- 
velop no  unnecessary  roots,  any  injury  to  them  results  in  a  lower  yield.     Four-inch 
pruning  six  inches  from  the  hill  reduced  the  yield  16.9  bushels.     (Table  4.) 

6.  The  cultivated  soil,  especially  in  periods  of  drouth,  is  too  loose  and  dry 
for  proper  root  development,  consequently  the  plant  is  deprived  of  the  food  which 
it  contains. 

7.  After  the  roots  are  well  distributed  thru  the  soil,  little  moisture  can  es- 
cape, even  from  uncultivated  land.      (Table  9.) 

8.  On  gray  silt  loam  on  tight  clay  in  southern  Illinois,  as  a  three-year  aver- 
age, preparation  of  seed  bed  gave  an  increase  of  21.5  bushels;   killing  weeds  by 
scraping  with  a  hoe  gave  a  gain  of  21  bushels  over  allowing  them  to  grow;  and 
fertilization  gave  an  increase  of  14.2  bushels.     Ordinary  shallow  cultivation  gave 
a  yield  of  31.2  bushels  per  acre,  while  killing  weeds  without  stirring  the  surface 
gave  31.5  bushels.     (Table  12.) 

9.  The  proper  type  of  cultivation  is  deep  enough  to  kill  the  weeds  but  shal- 
low enough  to  reduce  root  injury  to  the  minimum.     On  Illinois  soils  a  good  seed 
bed,  killing  weeds,  and  soil  enrichment  are  the  important  factors  in  growing  corn. 

10.  Cultivation  is  beneficial  for  aeration  of  heavy  soils,  clays  and  clay  loams. 
(Table  14.) 

II.  Cultivation  raises  soil  temperature  early  in  the  season  and  lowers  it  later. 
(Table  11.) 

12.  Subsoiling  on  gray  silt  loam  on  tight  clay  at  Odin  caused  a  decrease  of" 
2.7  bushels  per  acre.      (Table  15.) 

13.  Results  of  deep-tilling  tests  so  far  conducted  by  this  experiment  station 
do  not  warrant  recommending  the  purchase  and  use  of  deep-tilling  machines  in 
this  state. 


SOIL  MOISTURE  AND  TILLAGE  FOR  CORN 

BY  J.  G.  MOSIEE,  CHIEF  IN  SOIL  PHYSICS,  AND 
A.  F.  GUSTAFSON,  ASSOCIATE  IN  SOIL  PHYSICS 

The  common  impression  among  farmers  and  most  agricultural 
writers  is  that  cultivation  of  corn  is  necessary  as  a  means  for  con- 
serving moisture.  While  this  may  be  true  to  a  large  extent  in  sub- 
humid  and  semiarid  regions,  yet  in  humid  sections  this  purpose  in 
the  cultivation  of  corn  is  a  very  secondary  object. 

The  reader  is  asked  to  note  and  to  keep  in  mind  that  it  is  not  the 
purpose  of  the  authors  of  this  bulletin  to  recommend  specific  methods 
or  implements  to  be  used  in  the  cultivation  of  corn,  but  to  develop 
principles  that  should  be  observed  in  order  to  secure  the  best  results. 
The  investigations  reported  were  conducted  to  discover  why  corn  is 
cultivated,  and  no  one  should  assume  that  we  advocate  for  practical 
farming  the  substitution  of  hand  labor  for  horse  power,  but  only 
that  principles  should  guide  practice  toward  the  greatest  profits. 

KILLING  OF  WEEDS 

The  most  important  factor  in  the  growth  of  a  crop  of  corn  on 
fertile  soil  with  a  well-prepared  seed  bed  in  humid  regions  is  the  kill- 
ing of  weeds.  With  the  same  preparation  of  seed  bed,  corn  produced, 
as  an  eight-year  average,  7.3  bushels  per  acre  where  the  weeds  were 
allowed  to  grow,  and  45.9  bushels  where  the  weeds  were  kept  down 
without  any  cultivation.  This  gives  an  increase  of  38.6  bushels,  or 
say  $19.30  per  acre,  for  keeping  weeds  down.  Weeds  deprive  the 
plant  of  moisture,  light,  and  food,  all  of  which  are  absolutely  neces- 
sary for  the  production  of  crops.  Of  these  factors,  however,  the  one 
that  has  made  the  greatest  difference  is  that  of  plant  food.  Corn  has 
been  growrn  together  with  weeds,  but  irrigated  so  that  it  was  not  de- 
prived of  moisture,  yet  the  increase  from  irrigation,  as  a  four-year 
average,  was  only  3.8  bushels  per  acre.  Weeds  are  much  better  for- 
agers than  are  most  cultivated  crops;  and  it  would  be  just  as  rea- 
sonable to  expect  a  lamb  to  thrive  with  a  bunch  of  hogs  as  to  expect 
corn  to  compete  with  weeds. 

MOISTURE  AND  FOOD 

If  a  soil  is  in  good  tilth  and  there  are  no  weeds,  little  or  no  cul- 
tivation is  necessary.  If  it  is  in  poor  tilth  with  no  weeds  present, 
some  cultivation  may  be  necessary  for  aeration.  This  is  especially 

565 


566 


BULLETIN  No.  181 


[April, 


true  of  heavy  soils  or  those  containing  a  large  amount  of  clay.  In 
humid  climates  cultivation  of  corn  is  rarely  necessary  for  the  con- 
servation of  moisture  if  a  good  seed  bed  has  been  prepared.  After 
the  corn  has  become  twelve  inches  or  more  in  height,  the  roots  are 
so  completely  distributed  between  the  rows  that  it  is  difficult  for 
moisture  to  escape  from  the  soil,  for  it  is  captured  by  the  roots  in  its 
upward  progress.  As  an  average  of  eight  years'  investigations,  the 
soil  was  found  to  contain  no  more  moisture  where  the  corn  was  cul- 
tivated than  where  the  weeds  were  destroyed  without  cultivation. 
(See  Table  9.) 

Cultivation  should  be  as  shallow  as  possible  at  all  times,  altho 
deeper  stirring  is  permissible  the  first  time  than  later.  For  the  high- 
est yield,  cultivation  should  never  be  deep  enough  to  injure  the  roots. 
The  purpose  of  the  roots  is  to  get  plant  food  and  moisture,  and  as 
a  general  rule  plants  develop  no  more  than  are  necessary  for  this  pur- 
pose. The  injury  of  a  few  roots,  therefore,  may  stunt  the  corn.  It  must 
be  remembered,  too,  that  the  plowed  stratum  is  the  richest  part  of  the 
soil,  and  that  the  roots  will  naturally  develop  where  there  is  the  largest 
supply  of  plant  food.  Three-fourths  of  the  roots  of  the  corn  plant  are 
developed  in  the  plowed  soil.  For  this  reason  deep  plowing  in  both 
fall  and  spring  should  be  done  to  give  a  large  feeding  area. 

CULTIVATION  EXPERIMENTS  IN  OHIO 

Experiments  have  been  carried  on  at  several  stations  to  determine 
how  often  and  how  deep  corn  should  be  cultivated.  A  few  stations 
have  determined  the  effect  of  weeds  on  a  crop  of  corn.  The  first 

TABLE  1. — KESULTS  OF  CORN  CULTIVATION  AT  OHIO  EXPERIMENT  STATION, 

COLUMBUS,  OHIO* 
(Yields  in  bushels  per  acre) 


Kind  of  cultivation 

1883 

1884 

1885 

1886 

1887 

3-yr. 
av. 

Av.  %•  of 
No.  3 

1.  None,     weeds     allowed     to 
srrow    . 

21  7 

14.5 

6.4 

13.5 

.35 

6  7 

23.8 

2    Surface             

284 

91  3 

53.5 

1340 

52  7 

994 

3.  Ordinary,  4  or  5  times.  .  .  . 
4.  Ordinary,     excessive     num- 
ber   

49.8 

29.4 

82.4 
88.3 

56.0 
55.2 

20.00 
21.30 

52.8 
54.9 

100.0 
104.0 

5.  Ordinary,    three    times,    2 
days  apart   

895 

44.7 

18.90 

51.0 

96.5 

6.  Ordinary,    three    times,    4 

78.1 

47.0 

20.40 

48.5 

91.8 

7.  Ordinary,     three    times,    8 
<3ays  apart   

81.0 

56.4 

16.10 

51.2 

97.0 

8.  Ordinary,    three    times,   12 
days  apart  

94.0 

53.0 

18.80 

55.3 

104.7 

'Annual  Eeports  2  to  6. 

2The  yield  from  shallow  cultivation  is  taken  as  the  standard  and  represented 
as  100  percent ;  the  relative  yields  from  the  other  methods  of  cultivation  are  then 
expressed  in  percentage  of  this,  based  upon  all  comparable  yields. 


1915] 


SOIL  MOISTURE  AND  TILLAGE  FOR  CORN 


567 


to  carry  on  experiments  along  this  line  was  Ohio,  at  Columbus,  be- 
fore the  station  was  removed  to  Wooster.  Table  1  gives  the  results. 
Little  was  gained  by  a  large  number  of  cultivations.  Comparing 
the  average  yields  of  1885-1887,  we  find  54.9  bushels  for  excessive 
cultivation  as  against  52.8  bushels  for  four  ordinary  cultivations,  or 
an  increase  of  2.1  bushels.  The  effect  of  weeds  on  the  crop  as  shown 
in  these  results  was  very  striking.  Where  the  weeds  were  allowed 
to  grow,  8.7  bushels  of  corn  per  acre  were  produced,  as  a  four-year 
average,  but  where  the  weeds  were  kept  down  by  surface  cultivation 
the  yield  was  46.6  bushels,  or  37.9  bushels  increase. 

MISSOURI  EXPERIMENTS 

Table  2  gives  the  results  from  some  experiments  on  tillage  at  the 
Missouri  Station. 

TABLE  2. — RESULTS  OF  CORN  CULTIVATION  AT  MISSOURI  EXPERIMENT  STATION1 
(Yields  in  bushels  per  acre) 


Kind  of  cultivation 

1889 

1890 

Av. 

Av.  %  of 
No.  2 

1    None    scraped  with  hoe  

82.0 

45.7 

63.8 

95.3 

2    Shallow,  4  times  

80.1 

53.8 

66.9 

100.0 

3.  Deep,   4   times  

65.8 

41.2 

53.5 

80.0 

'Bulletin  14. 

Without  cultivation,  but  with  the  weeds  kept  down  by  scraping 
with  a  hoe,  the  average  yield  for  the  two  years  was  63.8  bushels  per 
acre,  while  for  shallow  cultivation  the  yield  was  66.9  bushels,  or  3.1 
bushels  increase.  Deep  cultivation,  compared  with  shallow,  shows  a 
loss  of  13.4  bushels  per  acre. 

INDIANA  EXPERIMENTS 

Table  3  gives  the  results  from  experiments  at  the  Indiana  Station 
in  which  cultivations  at  different  depths  were  compared. 

TABLE  3. — RESULTS  OF  CORN  CULTIVATION  AT  INDIANA  EXPERIMENT  STATION* 
(Yields  in  bushels  per  acre) 


Depth  of  cultivation 

1888 

1889 

1890 

1891 

2-yr. 
av. 

4-yr. 
av. 

One  inch  deep  

60.7 

56.6 

58  7 

Two  inches  deep  
Three    inches    deen.  . 

64.3 
64.6 

45.5 
41.8 

46.7 
46.4 

57.6 
50.2 

61.0 
57.4 

53.5 
50.8 

'Bulletin  39. 


EARLY  EXPERIMENTS  IN  ILLINOIS 

Professor  G.  E.  Morrow,  of  the  University  of  Illinois,  began  some 
experiments  in  1888  to  determine  the  value  of  cultivation  and  its  best 


568 


BULLETIN  No.  181 


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1015]  SOIL  MOISTURE  AND  TILLAGE  FOR  CORN  569 

depth  and  frequency ;  also  the  effect  of  root  pruning.  Table  4  gives 
his  results,  while  Table  5  gives  the  rainfall  by  months  during  the 
time  the  experiments  were  in  progress,  with  the  exception  of  the  year 
1888,  for  which  the  record  was  not  complete. 

Where  the  weeds  were  kept  down  by  scraping  with  a  hoe  without 
producing  a  mulch,  the  yield,  as  a  seven-year  average,  was  97.6  per- 
cent of  that  for  ordinary,  shallow  cultivation,  or  a  difference  of  1.7 
bushels  per  acre  in  favor  of  cultivation.  Deep  cultivation,  four  or 
five  times,  gave  96.9  percent,  or  2.2  bushels  less  than  shallow  cultiva- 
tion. Shallow  cultivation  twelve  to  fourteen  times  during  the  season 
gave  103.6  percent,  or  an  increase  of  2.5  bushels  per  acre,  while  deep 
cultivation  the  same  number  of  times  gave  91.7  percent,  or  a  decrease 
of  5.8  bushels  per  acre.  Compared  with  twelve  to  fourteen  shallow 
cultivations,  deep  cultivation  twelve  to  fourteen  times  gave  8.3  bushels 
decrease  per  acre. 

Another  experiment  carried  on  at  the  same  time  was  the  pruning 
of  the  roots  of  corn  at  a  distance  of  about  six  inches  from  the  hill. 
This  was  accomplished  by  placing  a  frame  twelve  inches  square  over 
the  hill  and  running  a  knife  around  the  outside  to  a  depth  of  four 
inches,  thus  cutting  the  roots  to  that  depth.  Where  shallow  cultiva- 
tion was  practiced,  this  pruning  resulted  in  a  decrease  of  12.5  bushels 
per  acre,  but  where  the  weeds  were  removed  by  scraping  with  a  hoe 
instead  of  by  shallow  cultivation,  the  yield  was  diminished  16.9  bush- 
els per  acre. 

LATER  EXPERIMENTS  AT  URBANA,  ILLINOIS 

The  results  obtained  by  Professor  Morrow  seemed  so  remarkable 
that  in  1906  and  1907  a  series  of  experiments  was  begun  to  demon- 
strate them,  and  at  the  same  time  to  obtain  data  on  some  other  fea- 
tures; namely,  the  damage  by  weeds,  the  value  of  a  seed  bed,  the 
effect  of  cultivation  on  moisture  and  temperature,  and  the  value  of 
irrigation  and  the  addition  of  plant  food  in  abundance.  The  results 
of  these  experiments  are  given  in  Table  6.  Table  7  gives  the  rainfall 
during  the  time  covered  by  the  experiments. 

The  soil  on  which  these  experiments  have  been  conducted  is  a 
brown  silt  loam,  the  ordinary  corn-belt  soil.  The  field  had  been  under 
cultivation  for  fifty  years  or  more,  but  during  this  time  no  fertilizer 
had  been  applied,  with  the  possible  exception  of  farmyard  manure. 

A  four-year  rotation  of  corn,  corn,  oats,  and  clover  has  been  prac- 
ticed. The  corn  stalks  and  both  crops  of  clover  have  been  removed. 
In  1912  and  1914  soybeans  were  grown  because  of  the  failure  of  clover. 
The  cultivating  was  done  with  the  three-shovel  cultivator  till  1912 ; 
and  since  then  the  surface  cultivator  has  been  used. 

While  the  total  rainfall  of  1911  and  1913  appears  to  be  approxi- 
mately normal,  yet  in  both  these  years  there  were  dry  periods  during 


570 


BULLETIN  No.  181 


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BULLETIN  No.  181 


[April, 


the  time  when  corn  should  have  been  making  its  greatest  growth  and 
needed  a  large  supply  of  moisture.  It  will  be  noted  that  in  1911  dur- 
ing June  .82  inch  of  rain  fell,  and  during  July  .62  inch,  while  in 
1913  in  May  .56  inch  fell,  in  June  1.67,  in  July  1.52,  and  in  August 
1.44  inches.  The  year  1913  was  the  driest  during  the  growing  time 
for  corn  since  the  rainfall  record  has  been  kept  at  the  University. 

Table  8  gives  the  amount  of  water  applied  to  the  irrigated  plots 
for  each  year  of  the  experiment,  and  also  the  rainfall  from  April  1 
to  August  31. 

It  will  be  seen  that  the  largest  amount  of  water,  16.91  inches,  was 
applied  during  1911,  and  the  next  largest,  12.85  inches,  in  1913.  The 
water  was  applied  in  amounts  equal  to  about  an  inch  of  rainfall,  by 
the  furrow  method  of  irrigation.  After  it  was  absorbed  and  the  soil 
had  become  sufficiently  dry,  the  furrows- were  partly  filled  with  loose 
soil  to  prevent  any  excessive  loss  by  evaporation.  The  yields  for  1913 
were  diminished  by  the  extreme  heat  during  the  time  when  pollina- 
tion was  taking  place.  A  storm  on  July  16,  1914,  damaged  the  corn 
on  all  plots  to  some  extent,  but  especially  where  the  growth  was  rank, 
as  on  the  fertilized  and  irrigated  plots. 


FIG.  1. — PLOT  1:   GROUND  NOT  PLOWED,  No  SEED  BED  PREPARED,  WEEDS  KEPT 
DOWN  BY  SCRAPING  WITH  A  HOE.    YIELD,  25.5  BUSHELS  (1911) 


1915] 


SOIL  MOISTURE  AND  TILLAGE  FOB  CORN 


573 


TREATMENT  OF  PLOTS 

Plot  1  was  plowed  but  once  during  a  rotation,  and  that  for 
oats.  The  vegetation,  such  as  clover  or  old  corn  stubs,  was 
removed  and  the  corn  planted  with  a  hoe.  The  weeds  were 
kept  down  by  scraping  with  a  sharp  hoe  so  as  to  produce  prac- 
tically no  mulch,  and  this  was  done  only  as  often  as  necessary 
to  kill  the  young  weeds. 

Plot  2  was  plowed  in  the  spring  about  6  inches  deep  for 
corn ;  a  good  seed  bed  was  prepared  before  planting  the  corn, 
but  no  cultivation  was  given.  The  weeds  were  kept  down  in 
the  same  way  as  on  Plot  1. 

Plot  3S  (Plot  3  until  1910)  was  plowed  in  the  spring  and 
a  good  seed  bed  prepared,  but  after  planting  time  the  weeds 
were  allowed  to  grow. 

Plot  3N  was  plowed  and  a  seed  bed  prepared ;  weeds  were 
allowed  to  grow  as  in  3S,  but  the  plot  was  irrigated  as  often 
as  necessary  to  keep  the  soil  in  a  moist  condition. 

Plot  4  was  treated  like  Plot  2,  except  that  the  corn  was 
cultivated  shallow  three  times  with  the  three-shovel  cultiva- 


FIG.  2. — PLOT  2:  GROUND  PLOWED,  SEED  BED  PREPARED,  WEEDS  KEPT  DOWN  BY 
SCRAPING  WITH  A  HOE.    YIELD,  39.8  BUSHELS  (1911) 


574 


BULLETIN  No.  181 


[April, 


tor  previous  to  1912,  and  with  the  surface  cultivator  since 
then.  Any  weeds  that  escaped  the  cultivator  were  pulled  or 
cut  out  with  a  hoe. 

Plot  5  was  treated  the  same  as  Plot  4,  except  that  the  crop 
was  irrigated  whenever  it  was  deemed  necessary. 

Plot  6  was  treated  similarly  to  Plot  5,  except  that  2  tons 
of  rock  phosphate  and  80  tons  of  manure  per  acre  were  ap- 
plied once  in  each  rotation  before  the  second  crop  of  corn. 

In  Table  6,  the  yield  of  the  cultivated  plot,  No.  4,  is  taken  as  the 
standard  for  computing  the  relative  yields  shown  in  the  last  column. 
On  Plot  1,  without  plowing  or  the  preparation  of  a  seed  bed  in  any 
way,  the  average  yield  for  eight  years  was  31.4  bushels  per  acre,  or 
80.1  percent  of  that  of  the  standard  cultivated  plot,  No.  4.  In  com- 
parison with  this,  on  Plot  2,  where  a  good  seed  bed  had  been  prepared 
arid  the  weeds  kept  down,  the  percentage  of  yield  was  117.1,  while 
the  average  actual  yield  for  the  eight  years  was  45.9  bushels,  or  an 
increase  of  14.5  bushels  per  acre  over  Plot  1.  This  represents  the 
value  of  the  seed  bed.  The  lowest  yield  of  Plot  2  was  33  bushels  in 
1908  and  the  highest,  75.5  bushels  in  1912.  It  would  seem  scarcely 
possible  that  such  a  yield  as  this  could  be  produced  without  cultiva- 


FIG.  3. — PLOT  3:  GROUND  PLOWED,  SEED  BED  PREPARED,  WEEDS  ALLOWED  TO  GROW. 
YIELD,  .8  BUSHEL  (1911) 


1915} 


SOIL  MOISTURE  AND  TILLAGE  FOR  CORN 


575 


tion;  yet  this  yield  was  the  highest  obtained  from  any  plot  except 
the  fertilized  one,  and  was  10.3  bushels  larger  than  that  produced  by 
cultivation.  It  will  be  noticed  that  Plot  2,  uncultivated,  gave  larger 
yields  three  out  of  the  eight  years  than  Plot  5,  the  cultivated  and 
irrigated  plot,  and  that  the  average  was  6.7  bushels  larger  than  for 
the  standard  cultivated  plot,  No.  4. 

On  Plot  3,  it  was  the  intention  to  see  what  would  be  the  effect  of 
weeds  on  the  corn  crop.  It  will  be  noticed  that  the  average  yield  here 
is  only  18.6  percent  of  that  of  the  cultivated  plot,  but  the  actual  yields 
varied  from  0  to  16  bushels.  The  results  of  Plot  3S  certainly  make  it 
very  evident  that  corn  cannot  thrive  with  weeds. 

In  order  to  determine  whether  it  was  a  lack  of  moisture  that  pro- 
duced the  low  yields  where  weeds  and  corn  were  grown  together, 
Plot  3  was  divided  in  1911,  and  the  north  half  was  irrigated  often 
enough  to  keep  the  soil  abundantly  supplied  with  moisture.  The  ef- 
fect was  quite  noticeable  both  on  the  corn  and  the  weeds,  but  as  an 
average  of  four  years  the  yield  was  increased  only  3.3  bushels  per  acre. 
It  must  therefore  appear  that  the  injury  done  by  weeds  is  not  largely 
due  to  the  moisture  that  they  take  out  of  the  soil,  but  to  some  other 
cause  or  causes. 


FIG.  4. — PLOT  4:  GROUND  PLOWED,  SEED  BED  PREPARED,  CULTIVATED  THREE  TIMES. 
YIELD,  34.5  BUSHELS  (1911) 


576 


BULLETIN  No.  181 


[April, 


It  would  be  well  to  compare  very  carefully  Plot  4  with  Plots  2 
and  5.  Plot  2,  uncultivated,  produced  6.7  bushels  more  corn  per  acre 
than  Plot  4  with  standard  cultivation;  but  the  fact  should  be  em- 
phasized that  to  obtain  such  a  result  requires  that  the  weeds  be  kept 
down.  Plot  5,  cultivated  and  supplied  with  all  the  moisture  that 
was  necessary,  produced,  as  an  average  of  eight  years,  only  1.8  bush- 
els more  than  the  uncultivated,  unirrigated  plot  where  weeds  were 
kept  down.  Irrigation  gave  an  increase  every  year  but  one.  This 
exception  was  in  1912,  when  only  a  small  amount  of  water  was  used. 
There  is  no  doubt  that  one  irrigation,  which  was  followed  within  a 
few  hours  by  a  heavy  rain,  did  no  good  and  even  may  have  damaged 
the  crop  to  some  extent. 

The  fertilized  plot,  No.  6,  gave  a  large  increase,  the  average  yield 
being  74.5  percent  above  that  from  standard  cultivation.  For  two 
years,  1908  and  1909,  this  plot  was  not  fertilized;  hence  the  yields 
for  these  years  have  been  omitted  in  the  table.  In  1914,  because  of 
the  heavy  growth,  the  crop  was  badly  damaged  by  a  storm.  The 
average  yield  for  the  seven  years  was  75.3  bushels  per  acre,  or  174.5 
percent  of  the  yield  from  the  standard  cultivated  plot  for  the  same 
years. 


FIG.  5. — PLOT  5:  GROUND  PLOWED  AND  SEED  BED  PREPARED,  CULTIVATED  THREE 
TIMES,  IRRIGATED  (16.91  INCHES  APPLIED).  YIELD,  55  BUSHELS   (1911) 


1015] 


SOIL  MOISTURE  AND  TILLAGE  FOR  CORN 


577 


The  fact  that  the  uncultivated  corn  produced  so  well  in  comparison 
with  the  cultivated  and  with  the  cultivated  and  irrigated,  shows  that 
cultivation  for  conservation  of  moisture  is  a  very  secondary  consid- 
eration in  this  climate  on  brown  silt  loam,  the  common  prairie  soil  of 
the  corn  belt.  On  Plot  2  the  crop  was  enabled  to  use  all  the  plowed 
soil  as  a  feeding  ground,  while  on  Plots  4,  5,  and  6  almost  half  the 
plowed  soil  was  disturbed  by  cultivation,  so  that  the  roots  of  the  corn 
were  either  injured  or  could  not  develop  in  that  stratum  because  of 
its  dry,  loose  character.  This  was  especially  true  on  Plot  4  during 
dry  seasons.  As  a  result,  the  plant  food  in  the  stirred  soil  was  of 
little  benefit  to  the  crop ;  and  the  conclusion  that  must  be  drawn  is 
that  the  cultivated  soil  is  of  much  greater  value  for  the  plant  food 
that  it  contains  than  for  the  conservation  of  moisture.  In  semiarid 
or  subhumid  regions  this  probably  would  not  be  true. 

A  study  of  the  moisture  content  of  the  plots  at  Urbana  was  made 
from  samples  taken  to  a  depth  of  40  inches  from  four  different  plots. 
The  samples  were  taken  in  the  spring  immediately  after  the  plowing 
was  done  and  once  each  week  until  the  corn  was  mature.  Table  9 
gives  the  results  in  percentage  of  total  moisture. 


FIG.  6. — PLOT  6 :  GROUND  PLOWED,  SEED  BED  PREPARED,  CULTIVATED  THREE  TIMES, 

IRRIGATED   (16.91  INCHES  APPLIED),  HEAVILY  FERTILIZED.  YIELD,  77.3 

BUSHELS  (1911) 


BULLETIN  No.  181 


[April, 


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Cultivation 

1.  Not  plowed  or  cultivated,  weeds  kept  down  by  scraping 
with  hoe  

2.  Plowed,  seed  bed  prepared,  no  cultivation,  weeds  kept 
down  by  scraping  with  hoe  

3S.  Plowed,  seed  prepared,  weeds  allowed  to  grow  

4.  Plowed,  seed  bed  prepared,  cultivated  shallow  3  times.  .  . 

1915]  SOIL  MOISTURE  AND  TILLAGE  FOR  CORN  579 

From  the  averages  given  in  the  table,  it  will  be  seen  that  the  sur- 
face stratum  of  the  unplowed  plot,  No.  1,  had  the  lowest  moisture 
content,  but  the  difference  among  the  plots  was  slight,  the  average 
being  only  1.0  percent  higher  in  the  plowed,  uncultivated  plot,  No.  2, 
.5  percent  higher  in  the  weed  plot,  No.  3S,  and  .7  percent  higher  in 
No.  4,  cultivated.  The  weed  plot,  both  in  1911  and  in  1913,  showed  a 
lower  moisture  content  than  the  other  plots — less  even  than  the  un- 
plowed one. 

Probably  a  better  idea  of  the  moisture  content  of  the  soil  can  be 
obtained  from  Table  10,  which  gives  the  lowest  moisture  content 
found  in  the  surface  soil  during  the  season. 

The  moisture  content  as  given  includes  both  hygroscopic  and 
capillary  moisture.  The  wilting  coefficient  of  this  type  of  soil,  i.e., 
the  point  at  which  the  plant  wilts  permanently,  or  where  the  plant 
has  used  all  of  the  available  water,  is  about  9.3  percent.  The  amount 
of  available  water  in  the  soil  at  any  time  is  the  difference  between 
the  actual  amount  present  and  the  wilting  coefficient.  From  the 
above  it  will  be  seen  that  but  little  available  moisture  was  in  the  soil 
at  certain  times  in  1911,  1913,  and  1914. 

The  temperatures  at  a  depth  of  2  and  4  inches  have  been  deter- 
mined once  each  week  during  the  last  five  years  on  Plot  1,  unplowed, 
and  on  Plot  4,  plowed  and  cultivated.  The  temperatures  were  taken 
three  times  a  day,  at  9  a.  m.  and  at  1 :45  and  4 :45  p.m.,  from  plow- 
ing time  till  the  corn  was  mature.  Table  11  gives  the  averages  of 
these  determinations. 

The  general  effect  of  tillage,  as  an  average  for  the  season,  was  to 
lower  the  temperature  from  .3  to  12.4  degrees.  A  single  exception 
was  the  average  temperature  taken  at  9  a.m.  for  the  two-inch  depth 
in  1909,  which  was  the  same  for  both  the  plowed  and  the  unplowed 
soil.  The  average  differences  in  temperature  between  the  plowed  and 
the  unplowed  plots  for  the  two-inch  depth  were  1.7  degrees  at  9  a.m., 

4.7  at  1 :45  p.m.,  and  3.9  at  4 :45  p.m.     The  average  differences  for 
the  four-inch  depth  were  1.3  degrees  at  9  a.m.,  2.2  at  1 :45  p.m.,  and 

1.8  at  4:45  p.m. 

Early  in  the  spring  the  effect  of  plowing  is  to  raise  the  tempera- 
ture of  the  soil  by  decreasing  the  amount  of  evaporation,  which  is  a 
cooling  process,  and  by  concentrating  the  heat  near  the  surface. 
Evaporation  takes  place  very  rapidly  from  unplowed  soil  because  of 
its  compactness  and  its  rather  high  moisture  content.  Later  in  the 
season,  however,  after  the  unplowed  soil  loses  some  of  its  moisture, 
the  tendency  is  for  it  to  become  warmer  than  the  plowed  and  culti- 
vated soil,  and  the  result  is  that  during  June,  July,  August,  and  Sep- 
tember the  relative  temperature  of  the  unplo.wed,  uncultivated  soil  is 
higher  from  one  to  twelve  degrees. 


580 


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SOIL  MOISTURE  AND  TILLAGE  FOR  CORN 


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ro 

1915]  SOIL  MOISTURE  AND  TILLAGE  FOR  CORN  583 


A  series  of  experiments  was  conducted  at  the  Fairfield  field  in 
Wayne  county,  on  the  gray  silt  loam  on  tight  clay,  the  common  prairie 
soil  of  southern  Illinois,  to  determine  the  relative  value  of  cultivation 
on  that  type  of  soil.  The  results  are  given  in  Table  12,  while  Table 
13  shows  the  monthly  rainfall  during  the  time  of  the  experiments. 

Comparing  Plots  1  and  2,  we  find  that  a  good  seed  bed,  as  prepared 
on  Plot  2,  increased  the  yield  by  215  percent  on  this  type  of  soil, 
while  on  the  brow,n  silt  loam  treated  similarly  at  the  University,  it 
gave  an  increase  of  46.2  percent.  Expressed  in  actual  yield,  the  in- 
crease at  Fairfield  was  12.9  bushels,  and  at  Urbana  14.5.  The  yields  as 
given  in  the  table  show  a  benefit  of  only  .2  bushel  from  cultivation 
after  the  seed  bed  was  prepared.  Taking  the  average  of  the  first  three 
years,  it  will  be  seen  that  the  uncultivated  plot  gave  an  actual  increase 
of  .3  bushel  over  the  cultivated.  The  fertilized  gave  an  increase  of  58.1 
percent  over  the  standard  cultivated. 

EXPERIMENTS  IN  MANY  STATES 

Bulletin  257  of  the  United  States  Bureau  of  Plant  Industry  gives 
data  recently  obtained  on  many  different  soils  in  twenty-eight  states. 
It  seems  unfortunate  that  the  types  of  soil  were  not  described  more 
fully  in  the  bulletin,  as  some  important  distinctions  in  regard  to  soils 
might  be  deduced.  In  six  years'  experiments  with  corn,  from  1905 
to  1911,  representing  112  tests,  the  average  yield  from  uncultivated 
plots  of  various  types  of  soil  expressed  in  percentage  of  similar  cul- 
tivated plots  was  99.8  percent.  This  figure  indicates  that  cultivation 
has  but  little  value  in  growing  a  crop  of  corn,  provided  the  weeds  are 
kept  down  in  some  other  way.  It  shows  that  the  principal  value  of 
cultivation  lies  in  the  killing  of  weeds  and  not  in  the  aeration  of  the 
soil  or  the  conservation  of  moisture.  We  find  that  in  subhumid  or 
semiarid  sections  the  average  yield  from  the  uncultivated  land  was 

TABLE  14. — CORN  YIELDS  OP  UNCULTIVATED  PLOTS  EXPRESSED  IN  PERCENTAGE  OP 
THE  YIELDS  OF  CULTIVATED  PLOTS  FOR  DIFFERENT  GROUPS  OF  SOIL  TYPES1 

(Average  of  six  years'  experiments,  1905-1911  )2 


Groups  of  soil  types 

Average  percent 

Clays  

92.6 

Clay  loams  

94.5 

Silt  loams  

102.4 

Sandy  loams  

105.7 

Average  of  groups  

98.8 

'Data  taken  from  U.  S.  Bur.  Plant  Indus.  Bui.  257. 

2This  includes  only  the  data  from  soils  which  could  be  classified. 


584 


BULLETIN  No.  181 


[April, 


85.9  percent  of  that  from  the  cultivated.  This  shows  a  greater  neces- 
sity for  cultivation  in  such  regions  than  in  humid  ones.  The  results 
obtained  from  some  of  the  different  types  of  soil  experimented  with 
are  reported  in  Table  14. 

It  will  be  noticed  that  the  value  of  cultivation  diminishes  as  the 
coarseness  of  the  soil  increases.  This  is  what  would  be  expected,  con- 
sidered theoretically.  The  fine-grained  soils,  such  as  clays  and  clay 
loams,  are  naturally  somewhat  poorly  aerated,  and  for  these  culti- 
vation would  be  of  value  for  aeration.  In  the  coarser  soils,  the  silt 
loams  and  sandy  loams,  aeration  is  naturally  better  and  hence  culti- 
vation is  not  so  beneficial. 

SUBSOILING 

Investigations  to  determine  the  value-  of  subsoiling  in  preparation 
for  corn  on  gray  silt  loam  on  tight  clay,  the  common  prairie  soil  of 
the  lower  Illinois  glaciation,  have  been  carried  on  for  eight  years  at 
the  Odin  field,  in  southern  Illinois.  Table  15  gives  the  results  of 
these  experiments.  The  form  of  plow  used,  shown  by  Fig.  7,  consists 
of  a  shoe  that  runs  in  the  bottom  of  the  furrow  made  by  the  ordinary 
mold-board  plow,  loosening  the  soil  but  not  throwing  it  upon  the 
surface. 


FIG.  7. — SUBSOIL  PLOW.  FOLLOWS  ORDINARY  PLOW  AND  LOOSENS  THE  SOIL  IN  THE 
BOTTOM  OF  THE  FURROW 

It  will  be  seen  that  with  every  soil  treatment  there  was  an  almost 
uniform  decrease  in  yield  for  subsoiling.  The  general  average  for 
eight  years  shows  a  decrease  of  2.7  bushels  per  acre.  The  alleged 


1915} 


SOIL  MOISTURE  AND  TILLAGE  FOR  CORN 


585 


benefit  of  subsoiling  is  the  increasing  of  the  water  capacity  of  soils  and 
of  their  ability  to  retain  water  during  dry  seasons.  Yet  in  1913  and 
1914,  both  of  which  were  very  dry  seasons,  this  method,  as  a  general 
average,  gave  only  the  very  slight  increases  of  .5  and  .7  bushel  respec- 
tively. The  subsoil  was  loosened  by  the  plow,  but  ran  together  as  soon 
as  it  was  wet  and  became  approximately  as  it  was  before.  The  experi- 
ments as  a  whole  show  that  subsoiling  on  this  type  of  soil  not  only  does 
not  pay,  but  is  a  losing  operation,  for  in  order  to  pay  for  the  extra 
work  involved  in  subsoiling,  at  least  a  three-bushel  increase  would  be 
necessary. 

NOTE. — Until  recently  the  amounts  of  limestone  and  crop  residues  on  the  Odin 
field  were  too  small  to  provide  for  the  adequate  liberation  of  potassium ;  but  where 
larger  supplies  of  limestone  and  organic  matter  are  provided  the  addition  of  potas- 
sium salts  produces  but  little  effect,  as  will  be  seen  from  the  results  of  the  Fairfield 
experiments  reported  in  Bulletin  123,  and  in  the  Appendix  of  county  soil  reports. 

TABLE  15. — CORN  YIELDS  IN  TILLAGE  EXPERIMENTS  ON  GRAY  SILT  LOAM  ON  TIGHT 

CLAY,  ODIN  FIELD* 

(Bushels  per  acre  as  an  average  of  two  plots) 


Soil  treatment 

1907 

1908 

1909 

1910 

1911 

1912 

1913 

1914 

8-yr. 
av. 

Not  Subsoiled 


None     

44.4 

35.5 

29.3 

28.8 

16.8 

26.1 

25 

43 

235 

Residues     

50.1 

33  ft 

30.4 

32.8 

19.0 

39.62 

3  9 

3  3 

265 

Residues,  lime  

473 

35.5 

ft9ft 

40.3 

24.7 

48.6 

4.1 

2.1 

28.9 

Residues,  lime,  phosphorus  

47.0 

39.9 

38.9 

38.7 

22.8 

494 

6  1 

2  0 

30  6 

Residues,  lime,  phosphorus,  potas. 

70.1 

76.1 

64.0 

79.8 

35.7 

65.43 

10.1 

3.1 

50.5 

Average  . 

51,8 

44,0 

38.3 

44,1 

ft38 

45.8 

53 

ft9 

3ft  0 

Subsoiled 


None     

37.6 

32.5 

24.1 

22.5 

133 

31  7 

3  2 

4  0 

21  1 

Residues     

43.2 

26.4 

27.2 

35.1 

19.9 

24.02 

3  6 

43 

22  9 

Residues,   lime    

473 

34.9 

28.5 

37.5 

22.7 

47.5 

4  1 

24 

28  1 

Residues,  lime,  phosphorus  

44.4 

45.9 

37.6 

39.8 

19  9 

28  1 

79 

2  5 

28  3 

Residues,  lime,  phosphorus,  potas. 

59.4 

60.3 

60.4 

85.6 

40.4 

48.52 

10.1 

5.0 

46.2 

Average   

46.3 

40.0 

35.5 

44.1 

23.2 

35.9 

5.8 

3.6 

29.3 

'The  east  half  Q|  each  plot  of  each  series  was  subsoiled  as  follows:  Series 
400  in  1907,  Series  300  in  1908,  Series  200  in  1909,  Series  100  in  1910,  and  so  on 
in  regular  succession. 

2Yields  from  single  plots,  as  the  corn  in  two  plots  in  1912  was  badly  damaged 
by  water. 

DEEP  TILLING 

Farmers  are  frequently  urged  to  purchase  a  machine  for  plowing 
to  a  depth  of  12  to  15  inches.  There  is  little  doubt  that  under  certain 
conditions  of  soil  and  climate  such  plowing  would  be  beneficial;  but 
the  results  obtained  by  the  Experiment  Station  in  this  state  with  the 
deep-tilling  machine  on  the  common  prairie  soil  of  the  corn  belt  do 


586  BULLETIN  No.  181  [April, 

not  warrant  recommending  its  purchase.  Experiments  have  been 
started  also  on  gray  silt  loam  on  tight  clay,  in  southern  Illinois,  to 
determine  the  comparative  value  of  ordinary  plowing,  subsoiling,  deep 
tilling  (plowing  12  to  15  inches  deep),  and  dynamiting  the  subsoil. 
Only  one  year's  results  have  been  secured,  and  no  conclusions  are  as 
yet  justified. 


MVERSITYOFILLINOIS-URBANA 


C001 


166-181  1914-15 


' 


3011201*28436 


>*•"«** 


i 


